ability to run code and check output in tests

tests/TestCase.newt

@@ -0,0 +1,76 @@
+module TestCase
+
+-- I'm testing cases here, but using examples carefully design to be
+-- simple case trees. Patterns are a var or a constructor applied to vars.
+
+-- There are indexes below, but we're got pulling constraints out of them yet.
+
+
+
+data Nat : U where
+  Z : Nat
+  S : Nat -> Nat
+
+data Vect : Nat -> U -> U where
+  Nil : {a : U} -> Vect Z a
+  Cons : {a : U} {n : Nat} -> a -> Vect n a -> Vect (S n) a
+
+plus : Nat -> Nat -> Nat
+plus = \ n m => case n of
+  Z => m
+  S k => S (plus k m)
+
+-- Example from Jesper talk (translated to explicit case tree)
+max : Nat -> Nat -> Nat
+max = \ n m => case n of
+  Z => m
+  S k => case m of
+    Z => S k
+    S l => S (max k l)
+
+length : {a : U} {n : Nat} -> Vect n a -> Nat
+length = \ v => case v of
+  Nil => Z
+  Cons x xs => S (length xs)
+
+data Unit : U where
+  MkUnit : Unit
+
+-- This should fail (and does!)
+-- bar : Vect (S Z) Unit
+-- bar = (Cons MkUnit (Cons MkUnit Nil))
+
+data Bool : U where
+  True : Bool
+  False : Bool
+
+not : Bool -> Bool
+not = \ v => case v of
+  True => False
+  False => True
+
+
+not2 : Bool -> Bool
+not2 = \ v => case v of
+  True => False
+  x => True
+
+and : Bool -> Bool -> Bool
+and = \ x y => case x of
+  True => y
+  False => False
+
+-- FIXME - a case is evaluated here, and I don't know why.
+
+nand : Bool -> Bool -> Bool
+nand = \ x y => not (case x of
+    True => y
+    False => False)
+
+-- -- this should be an error.
+-- foo : Bool -> Bool
+
+data Void : U where
+
+foo : Int
+foo = 42